1. Field of the Invention
The present invention relates to a liquid crystal display which employs a display mode utilizing birefringence and, more particularly, to a liquid crystal display employing a display mode in which a liquid crystal material forms bend configuration.
2. Description of the Related Art
In a liquid crystal display using an optically compensated birefringence (OCB) mode, a liquid crystal material is caused to form bend configuration, and the tilt angles of liquid crystal molecules are changed near each alignment layer, thereby changing the optical retardation of an optical filter layer. Because of utilizing bend configuration, the OCB-mode is one of the display mode capable of realizing a high response speed and a wide viewing angle, and has attracted attention in recent years.
As described above, bend configuration is essential in the OCB-mode. However, bend configuration is difficult to stabilize as will be explained below.
That is, a liquid crystal material of OCB-mode liquid crystal display forms splay configuration in an initial state in which the power supply is off. Therefore, a process of changing splay configuration to bend configuration is necessary every time energizing the display. Due to uncontrollable factors regarding to the shape of the substrate surface or the electric field distribution, an unchanged region sometimes remains in the optical filter layer. In addition, splay configuration is intrinsically more stable than bend configuration under usual surface alignment conditions. Accordingly, if a voltage is not continuously applied, bend configuration may change to splay configuration.
To solve this problem, Japanese Patent No. 3459916 describes a structure in which the opposed surfaces of an active matrix substrate and counter substrate are inclined to each other. Japanese Patent No. 3459916 also describes a structure in which grooves having a V-shaped section are formed on the opposed surfaces of the active matrix substrate and counter substrate, such that the cell gap at a position corresponding to the center of a pixel electrode is wider than the cell gap at positions corresponding to the two ends of the pixel electrode.
Bend alignment can be stabilized by the use of these structures. However, the present inventors have found that a liquid crystal display which stabilizes bend configuration by using the above structures readily causes stripe-like modulation in the display brightness.